The Remington 870 currently has the magazine tube cap retaining system that utilizes a plastic plug with "teeth" that mates to "teeth" on the inside of the screw on metal end cap. My 870 that was purchased 14 years has this end cap retaining system. My much older 870 utilizes a small indented spring assisted metal ball located on the barrel ring that mates to the "dimples" on the perimeter of the end cap then used.
Question: Does anyone know approximately when Remington started utilizing the indented spring assisted metal ball end cap retention system? What I'm actually trying to find out is if the 870 has always had some form of end cap retaining system - or was it an added feature incorporated along the way, and if so, when was it incorporated. Many thanks.